Auxins such as dicamba and 2,4-Dichlorophenoxyacetic acid (2,4-D) may volatilize when used as herbicides. In this work, a fast, straightforward method to determine the relative volatility of auxin formulations is presented. The method uses a sprayed soil substrate in a disposable closed dome system. For a 24-h period, air is drawn out of the closed dome and passed through a polyurethane foam (PUF) plug where any volatile auxin is trapped. The auxin is extracted from the PUF with methanol, and the resultant extract solution is analyzed for the auxin by liquid chromatography-mass spectrometry (either LC-MS or LC-MS\MS). The data are then used to determine the relative volatility of the formulations.